Rats passively exposed to tobacco smoke become dependent on nicotine, according to a new study by Dr. Adrie Bruijnzeel and colleagues from the University of Florida in the US. Their findings of how rats' brains respond to exposure to tobacco smoke have implications for the study of the effects of tobacco smoke on the human brain even from passive exposure to other smokers, and for future studies testing new treatments for tobacco addiction. Their work has just been published online in Springer's journal Psychopharmacology.